1. Field of the Invention
The present invention relates to a dust-proof filter unit, an image pickup apparatus, and a projection image display apparatus, and particularly to an image pickup apparatus equipped with an image pickup device unit including an image pickup device which generates an image signal corresponding to a light irradiated onto a photoelectric conversion surface, and optical apparatuses such as a projection image display apparatus which forms an optical image in response to image information by modulating a light flux emitted from a light source by means of an image forming element, and enlarges and projects the optical image.
2. Description of the Related Art
Heretofore, image pickup apparatuses such as a digital camera have been generally commercialized and in wide spread use, which is an optical apparatus equipped with an image pickup device unit including a solid image pickup device (for example, a charge coupled device (CCD); hereinafter, simply referred to as an image pickup device) which receives an object image formed based on a light flux from an object (hereinafter, referred to as an object light flux) that has passed through a photographing optical system, and generates an image signal corresponding thereto.
Some of such digital cameras are equipped with a finder apparatus for observing an object to be photographed prior to a photographing operation. An example of such finder apparatuses is an optical finder apparatus of a single lens reflex type, which is configured to allow the observation of an optical image (object image) formed by for example a photographing optical system, and which can lead the object light flux that has passed through the photographing optical system to a photoelectric conversion surface of an image pickup device upon a photographing operation.
In recent years, digital cameras of single lens reflex type featuring interchangeable lenses are becoming in common use, in which by providing an optical finder apparatus of a single lens reflex type and arranging the photographing optical system to be detachable with respect to the camera body, it is made possible for a user to freely detach and replace the photographing optical system as desired thereby selectively using multiple types of photographing optical systems for a single camera body.
Such digital cameras featuring interchangeable lenses have a risk in that dusts etc. floating in the air enter into the camera body while the photographing optical system concerned is detached from the camera body. Further, since various mechanisms which operate mechanically, such as a shutter mechanism and an aperture mechanism are disposed in the camera body, minute debris etc. may be produced from such various mechanisms during the operation thereof.
During a photographing operation in which the shutter mechanism is kept open, the photoelectric conversion surface of the image pickup device, which is disposed in the rear of the photographing optical system, is exposed to the air inside the camera. This may cause the dusts and minute debris etc. produced as described above to adhere to the photoelectric conversion surface of the image pickup device.
Thus, the dusts and minute debris etc. that have adhered to the photoelectric conversion surface may have adverse effects such as causing an undesired shadow on the image represented by an image signal generated by the image pickup device.
Accordingly, in Japanese Patent Laid-Open No. 2003-348401, the present applicants proposed and put into practical use a technique which allows to remove the dusts adhering to the photographing lens side surface of an optical device, by disposing an optical element (a dust-proof member) on the front face side of a photoelectric conversion element (an image pickup device) so that the space between the optical element and the photoelectric conversion element is sealed, and causing the optical element to vibrate by means of excitation means.
Further, in Japanese Patent Laid-Open No. 2002-204379, the present applicants proposed a technique which allows to remove the dusts adhering to the surface of an optical element, by proving a dust-proof member (the optical element) on the front face side of a photoelectric conversion element (an image pickup device), and a stacked piezoelectric body which provides vibration in a predetermined direction to the dust-proof member, one end of which is fixedly disposed to a predetermined portion of the dust-proof member, and to the other end of which a weight member is fixedly attached, and by applying a periodic voltage to the stacked piezoelectric body to cause the dust-proof member to vibrate along the optical axis of a photographing lens.
On the other hand, although image pickup devices sealed in a package (for example, called as a packaged CCD) are in wide spread use as the image pickup device for conventional digital cameras, recently, other than such form of image pickup devices, marketing of CCD chips in a bare state so called a bare-chip CCD has been proposed.
In such a bare-chip CCD, since dusts or the like are more likely to adhere to the photoelectric conversion surface thereof, for example, Japanese Patent Laid-Open No. 09-130654 discloses proposals on a configuration which enables to shake off the dusts or the like adhering to the photoelectric conversion surface of the CCD by providing a piezoelectric element between a bare-chip CCD and a substrate for mounting the bare-chip CCD, and vibrating the bare-chip CCD itself by applying a predetermined voltage to the piezoelectric element; or a configuration which allows to remove the dusts or the like adhering to the photoelectric conversion surface of the CCD concerned by providing an optical member in front of the photoelectric conversion surface of a bare-chip CCD, arranging the optical member and the bare-chip CCD to be sealed inside a hollow cylindrical member, and causing the bare-chip CCD to vibrate by means of a piezoelectric element provided in the back of the bare-chip CCD.
On the other hand, in recent years, various kinds of optical apparatus are proposed and put into practical use, including a projection image display apparatus, so called a projector, which is configured such that a light flux emitted from a light source is modulated to form an optical image in response to image information by means of an image forming element such as a liquid crystal display element, and thus formed optical image is enlarged and projected onto a screen etc.